For access network deployment, such as fiber to the home (FTTH) or fiber to the curb (FTTC), it is desirable to use only one fiber optic cable or wave guide in order to reduce costs. This is particularly so because the length of the cable may reach 20 kilometers in such deployments and a conventional approach, using a two-fiber transceiver with a duplex-fiber, would be much more costly. However, providing bi-directional communication over a single fiber optic cable using photons or light signals and over such distances is challenging.
In bi-directional communication over a single fiber optic cable, transmitting and receiving of photons or light signals is performed over the same single fiber optic cable or wave guide. In order to do so, the transmit data and receive data are multiplexed onto the same single fiber optic cable using two different wavelengths or frequencies of light. Input or transmit data is multiplexed onto the fiber optic cable while output or receive data is de-multiplexed from the fiber optic cable. The input or transmit data path using one wavelength of light is often referred to as the transmit channel. The output or receive data path using another wavelength of light is often referred to as the receive channel. Data is multiplexed onto the transmit channel and data is demultiplexed off of the output channel at each end of the single fiber optic cable.
At each end of a typical optical data link is an optical transceiver to transmit and receive data over the respective transmit and receive channels. The optical transceiver at each end needs to be capable of supporting bi-directional communication over a single fiber optic cable for such deployments. In order to provide efficient bi-directional communication over the same single fiber optic cable, it is desirable to minimize optical crosstalk between the transmit and receive channels while providing good coupling and minimal manufacturing costs in an optical transceiver.